Sam Wylie-Harris looks at the key issues surrounding the forthcoming vote on abortion and talks to those for and against a change in the law.
For the majority of women, a positive preg-nancy test should be one of the happiest days of their life, but if it isn't exactly what they'd planned, or they feel unable to cope with the prospect of motherhood, a termination is considered by many to be the most sensible option.
So much so that last year 200,000 women in the UK chose to have one. In fact, Britain is fast becoming the abortion capital of Europe, second only to the Ukraine.
The vast majority - 89 per cent - take place within the first three months of pregnancy and less than two per cent are carried out between 20 and 24 weeks.
Abortion became legal in the UK in 1967 when the Abortion Act was passed, allowing terminations up to 28 weeks of pregnancy - then believed to be the time at which a foetus became viable. In 1990 the limit was lowered to 24 weeks.
MPs and pro-life activists are now campaigning for the 24-week time limit to be re-duced to 20 weeks, and on Tuesday, the first vote on abortion law in 18 years will take place in the House of Commons.
David Cameron and several Conservative frontbenchers have said they would vote for a reduction of the 24-week limit. Among other changes proposed to the law is a five-day 'cooling off' period for women, in an attempt to bring Britain into line with 26 countries which have introduced "informed" consent.
Can a foetus survive if born at 24 weeks? Pro-life campaigners have been spurred on in this latest campaign by advances in scien-tific research and increased survival rates of premature babies.
However, according to the latest report by the British Medical Association: "Over the past 12 years there has been no improvement in survival of babies born before 24 weeks' gestation."
In response to suggestions that the current limit for abortion should be lowered because of improvements in the medical care and survival of premature babies, the BMA says: "There is a lack of evidence to confirm whether survival of these babies has improved in recent years."
Professor David Field from the Neonatal Unit at the Royal Infirmary, Leicester, was be-hind the report.
He says: "We produced this paper to provide solid data on survival at the lowest gestations in recent years. The findings are clear: Significant improvement in survival at 24 and 25 weeks gestation; no improvement in survival at 22 and 23 weeks gestation.
"As a neonatologist I do not see a link between these data and the abortion debate, but if those involved do see survival as relevant then these data should form the basis for a rational discussion."
This report, published in the British Medical Journal (BMJ), is the latest published data on the survival of premature babies from the Trent region, but the authors say it is reasonably representative of the UK as a whole.
It is backed up by preliminary findings from a major nationwide study called EPICure Two, which reveals there has been no improvement in survival rates for babies born before 24 weeks in the past ten years - although the research is not yet complete.
Conservative MP Nadine Dorries is head-ing up the official 20-week limit parliamentary campaign (the20weekscampaign.org). She says she has the backing of David Cameron, Dr Liam Fox, Iain Duncan Smith, Michael Howard, and more than 200 MPs.
A former nurse, she rejects the report in the BMJ: "Babies that are born prematurely who go into hospital and receive neo-natal care have much better outcomes than those quoted in the report.
"We're going back 12 years in some of these statistics.
"If a woman goes into premature labour in a hospital which has a neo-natal unit, you are actually looking at something like 45 per cent of 22 weekers and 40 per cent of 23 weekers who survived well.
"The 16 hospitals which were studied in the BMJ report didn't have neo-natal services. Women went into labour and then the babies were transported up to 30 or 40 miles away to a neo-natal unit. Premature babies need to have assistance very quickly otherwise they will die."
The Royal College of Obstetricians and Gynaecologists, the British Medical Association and the Royal College of Nursing all strongly favour upholding the current time limit.
When does a foetus start to feel pain? Hard-line anti-abortionists believe there is no difference between getting rid of an unwanted pregnancy at eight weeks or at 24 weeks, and that a foetus is a person from the moment of conception.
For those standing on the middle ground, how does a woman know when the foetus inside her has become a human being, another person?
Conflicting reports can be confusing. The general medical consensus is that a foetus does not feel pain before at least 26 weeks because the neurological development necessary to feel pain has not yet developed.
However, Nadine Dorries argues: "The latest neo-natal research shows a baby inside the uterus feels physical pain at 18 weeks.
"If a baby were allowed to be born and it could stand a chance of living, I think we've reached a point where a baby's right to life reaches parity with the mother's right to choose."
Are vulnerable women going to suffer? Marie Stopes International is the UK's largest provider of abortion services outside the NHS (mariestopes.org). It gives advice on family planning, contraception, abortion services and post abortion care.
Anne Quesney, head of advocacy at Marie Stopes, says: "Late abortions are extremely rare but sometimes desperately needed by a small number of women facing complex personal circumstances.
"We believe that these women should be trusted to make the decision and deserve our support."
An amendment to the abortion law could see the most vulnerable women suffer, she believes.
"As well as teenagers in denial until late into their pregnancy, there are all sorts of tragic cases.
Anne explains: "There are those who may have been abused by a partner and were scared to come forward.
"Sometimes the result of a mid-pregnancy scan can show the foetus is severely abnormal and then there are women whose circumstances have changed.
"Their partners left them and they find them-selves unemployed, on their own and unable to look after a child.
"No woman wants to have an abortion in the first place, let alone after 20 weeks.
"This is not a procedure a woman or doctor engage in willy nilly, it's something serious, it's something complex, and to force those women to carry on their pregnancy against their will is just cruel and so wrong.
"When an abortion is performed after 20 weeks these are exceptional circumstances."
Ann Furedi, chief executive of the British Pregnancy Advisory Service, says: "Abortion can be a complex, social and moral issue, but many of our politicians feel more comfortable voting on the scientific evidence on the sur-vival of premature babies."